1. FIELD OF THE INVENTION
The present invention relates to a composition for the lubricating treatment of synthetic fibers. More particularly, the invention relates to a composition for the lubricating treatment of synthetic fibers which are to be subjected to a subsequent heating process, which composition has an appropriate lubricating effect and possesses thermal stability at high temperatures.
2. DESCRIPTION OF THE PRIOR ART
In the manufacture of synthetic fibers, filaments prepared by the melt-spinning process are heated for drawing or are subjected to heat setting to improve the properties thereof. Further, in the manufacture of bulky yarns, such as false twisted yarns, a heat treatment is ordinarily conducted for setting the bulky configuration. In these processes, the filaments or yarns are often treated at considerably high speeds. Accordingly, the lubricating compositions applied to filaments or yarns to facilitate such steps as spinning, drawing and processing smoothly are required to have high heat resistance, high lubricity and high antistatic property.
As lubricating agents for complying with the foregoing requirements and suitable for use in combination with an emulsifier, an antistatic agent or the like, there have heretofore been employed mineral oils, esters of higher alcohols with higher fatty acids, esters of higher alcohols with dibasic acids such as adipic acid and sebacic acid or other fatty acids, and esters of trimethylolpropane, ethylene glycol or the like with fatty acids.
These conventional lubricating agents, however, are insufficient in heat resistance. Accordingly, they generate smoke during the heat drawing process or false twisting step whereby to form tar-like substances on the heaters, and therefore, the passages for yarn are considerably contaminated which in turn causes such troubles as monofilament winding or yarn breakage. As a result, it becomes impossible to perform the drawing or false twisting operation smoothly and the machine has to be stopped for cleaning. Thus, various troubles are caused and the operational efficiency is reduced.
As means for preventing the formation of tar-like substances on heaters, there has been proposed a method in which a specific polyalkylene glycol is incorporated as a lubricating component (see, for example, Japanese Patent Publication No. 50657/72, Japanese Patent Application Laid-Open Specification No. 22793/73 and Japanese Patent Publication No. 33793/73).
Such specific polyalkylene glycol has the preferred property that no tar-like substance is formed when it is heated on a heater. However, it is readily oxidized and decomposed by heat or light so as to generate a bad smell or it is defective because it deteriorates with the passing of time. Further, compounds of this type do not have a sufficient affinity with hydrophobic fibers such as nylon fibers and polyester fibers. Accordingly, in the manufacture of fibrous products for which a high strength is required, such as tire cords, hoses, belts and fishing nets, lubricating agents of this type are insufficient in their capacity of protecting filaments and yarns from severe heating and friction.
Our assignee previously developed compounds for a lubricating composition for synthetic fibers intended to be treated by a heating process, which compounds have excellent heat stability, and disclosed these compounds in Japanese Patent Publication No. 29474/72 and Japanese Patent Application Laid-Open Specification No. 70397/76.
The lubricating agents used in these prior inventions are diesters formed by adding an alkylene oxide to bisphenol A and esterifying the adduct with a higher fatty acid or the like. These diesters have the formulas (II) or (III): ##STR2## wherein R.sub.1 and R.sub.2 each is a saturated or unsaturated hydrocarbon group having 8 to 22 carbon atoms, and m and n each are integers of at least 1, with the proviso that the sum of m and n does not exceed 50.
Lubricating compositions containing these compounds have a very excellent heat stability, and the foregoing defects involved in the conventional lubricating compositions were eliminated by using these compounds.
However, it has been found that these compounds are disadvantageous because the friction of fibers, especially with metals or porcelains, is very high and the lubricity is insufficient. Accordingly, the lubricity should be improved for some uses.
It may be supposed that the lubricity will probably be improved by mixing an ester formed by reaction between a monohydric or polyhydric alcohol and a monobasic or dibasic fatty acid with a compound of the formula (II) or (III) (hereinafter referred to as "bisphenol type ester" or "bisphenol type lubricant"). It has been found that the smoothness can be improved by this modification, but the heat resistance is drastically degraded.
It is, therefore, a primary object of the present invention to provide a composition for the lubricating treatment of synthetic fibers in which the foregoing defects are eliminated or ameliorated, namely, a lubricating composition for synthetic fibers in which the generation of smoke and the formation of tar-like substances are remarkably controlled and which has an excellent heat stability and imparts good lubricity to synthetic fibers.